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Pattern recognition of stroke subtypes

The two broad categories of stroke, hemorrhage and ischemia, are diametrically opposite conditions: hemorrhage is characterized by too much blood within the closed cranial cavity, while ischemia is characterized by too little blood to supply an adequate amount of oxygen and nutrients to a part of the brain.



Intracerebral hemorrhage _ Bleeding in intracerebral hemorrhage (ICH) is usually derived from arterioles or small arteries. The

bleeding is directly into the brain, forming a localized hematoma that spreads along white matter pathways. Accumulation of blood occurs over minutes or hours; the hematoma gradually enlarges by adding blood at its periphery. The hematoma
continues to grow until the pressure surrounding it increases enough to limit its spread or until the hemorrhage decompresses itself by emptying into the ventricular system or into the cerebrospinal fluid (CSF) on the pial surface of the brain.

The most common causes of ICH are hypertension, trauma, bleeding diatheses, amyloid angiopathy, illicit drug use (mostly amphetamines and cocaine) and vascular malformations Less frequent causes include bleeding into tumors, aneurysmal rupture, and vasculitis.

The earliest symptoms of ICH relate to dysfunction of the portion of the brain that contains the hemorrhage.

The neurologic symptoms usually increases gradually over minutes or a few hours. In contrast to brain embolism and SAH, the neurologic symptoms do not begin abruptly and are not maximal at onset.

Headache, vomiting, and a decreased level of consciousness develop if the hematoma becomes large enough to increase intracranial pressure or cause shifts in intracranial contents. These symptoms are absent with small hemorrhages; the clinical presentation in this setting is that of a gradually progressing stroke.

ICH is characterised by Haematoma formation in the brain tissue.

Subarachnoid hemorrhage - The two major causes of SAH are rupture of arterial aneurysms that lie at the base of the brain, and bleeding from vascular malformations that lie near the pial surface. Bleeding diatheses, trauma, amyloid angiopathy, and illicit drug use are less common.

Symptoms of SAH begin abruptly in contrast to the more gradual onset of ICH. The sudden increase in pressure causes a cessation of activity (eg, loss of memory or focus or knees buckling). Headache is an invariable symptom and is typically instantly severe and widespread, the pain may radiate into the neck or even down the back into the legs. Vomiting occurs soon after onset. There are usually no important focal neurologic signs unless bleeding occurs into the brain and CSF at the same time (meningocerebral hemorrhage).

Two major cause of SAH are rupture of arterial aneurysm and bleeding from arterial malformation.

Headache is an invariable symptomof SAH and symptoms are abrupt in onset without focal neurological deficit.

Brain ischemia - There are three main subtypes of brain ischemia.

Thrombosis _ Thrombotic strokes can be divided into either large or small vessel disease. These two subtypes of thrombosis are worth distinguishing since the causes, outcomes, and treatments are different.

1. Atherosclerosis is by far the most common cause of in situ local disease within the large extracranial and intracranial arteries that supply the brain. Vasoconstriction (eg, with migraine) is probably the next most common, followed in frequency by arterial dissection and traumatic occlusion.

2. The most common cause of obstruction of the smaller arteries and arterioles that penetrate at right angles to supply the deeper structure within the brain (eg, basal ganglia, internal capsule, thalamus, pons) is lipohyalinosis, blockage of an artery by medial hypertrophy, and lipid admixed with fibrinoid material in the hypertrophied arterial wall. A stroke due to obstruction of these vessels is referred to as a lacunar stroke. Lipohyalinosis is most often related to hypertension but aging may play a role.

In patients with thrombosis, the neurologic symptoms often fluctuate, remit, or progress in a sputtering fashion.

Embolism - Embolic strokes are divided into four categories

  • Those with a known source that is cardiac

  • Those with a possible cardiac or aortic source

  • Those with an arterial source

  • Those with a truly unknown source in which tests are negative.

The symptoms depend upon the region of brain rendered ischemic. The embolus suddenly blocks the recipient site so that the onset of symptoms is abrupt and usually maximal at the start. Unlike thrombosis, multiple sites within different vascular territories may be affected when the source is the heart (eg, left atrial appendage or left ventricular thrombus) or aorta. Treatment will depend upon the source and composition of the embolus.

Systemic hypoperfusion - Reduced blood flow is global and does not affect isolated regions. The reduced perfusion can be due to cardiac pump failure caused by cardiac arrest or arrhythmia, or to reduced cardiac output related to acute myocardial ischemia, pulmonary embolism, pericardial effusion, or bleeding. Hypoxemia may further reduce the amount of oxygen carried to the brain.

Symptoms of brain dysfunction typically are diffuse and nonfocal in contrast to the other two categories of ischemia. The neurologic signs are typically bilateral, although they may be asymmetric when there is preexisting craniocerebral vascular occlusive disease.

  • Thrombosis generally refers to local in situ obstruction of an artery.

  • Embolism refers to particles of debris originating elsewhere that block arterial access to a particular brain region

  • Systemic hypoperfusion is a more general circulatory problem, manifesting itself in the brain and perhaps other organs.